HAZARD ASSESSMENT OF DEBRIS FLOWS INITIATED BY BREACH OF SMALL EARTH DAMS IN BRITISH COLUMBIA

ABSTRACT: Small earth dams perched high above the main valley floor pose a potential risk for destructive debris flow generation if they breach. A small outburst can trigger a large debris flow. The Testalinden dam failure in BC demonstrates the destructive power of a debris flow triggered by the water released by a breach through a small, poorly maintained dam. The debris flow destroyed homes and damaged properties. This paper presents a methodology for preliminary assessment of debris flow potential caused by the breaching of small earth dams. The predicted peak breach outflow, the creek gradient, and the estimated height of the water, or outflow per unit width in the creek channel are used as criteria to delineate possible locations along a creek where a debris flow may initiate. Dam failure consequence classification should incorporate assessment of breach-induced debris flows.